Grammar. a bound inflectional or derivational element, as a prefix, infix, or suffix, added to a base or stem to form a fresh stem or a word, as -ed added to want to form wanted, or im- added to possible to form impossible.

a linguistic element added to a word or root to produce a derived or inflected form: -ment in establishment is a derivational affix; -s in drowns is an inflectional affix See also prefix, suffix, infix